1. Field of the Invention
The present invention relates to an image forming apparatus, a control method therefor, and a program for implementing the control method, and more particularly to an image forming apparatus which carries out electric power saving control and job scheduling for a plurality of processing devices connected respectively to a sheet feed side and a sheet discharge side of the image forming apparatus, a control method therefor, and a program for implementing the method.
2. Description of the Related Art
Conventionally, there have been image forming apparatuses such as printers, facsimile machines, and copying machines, having a plurality of sheet feed devices (more generally, pre-processing devices) such as a sheet feed deck and an inserter on a sheet feed side thereof, and a plurality of post-processing devices such as a finisher and a sorter on a sheet discharge side thereof. An image forming apparatus of this type turns on all pre-processing devices and post-processing devices before a job is carried out in order to bring these processing devices in operable states. On this occasion, if there are processing devices which are not used to carry out the job, these devices waste electric power.
Japanese Laid-Open Patent Publication (Kokai) No. H08-295065 discloses an image forming apparatus comprised of a sorter section, which is a function block constituting a post-processing device, and other function blocks. The function blocks except for the sorter section include a scanner section, an image processing section, an image forming section, a FAX section, and an expanding section that expands image data and then outputs the expanded image data to the image processing section. The sorter section sorts printed sheets output from the image forming section into predetermined trays. The image forming apparatus has switch circuits provided for the respective function blocks to independently supply electric power to the respective function blocks, thereby reducing electric power consumption. For example, the switch circuits corresponding, respectively, to the sorter section, the image processing section, the image forming section, and the expanding section are closed in a sort mode to supply electric power to these function blocks while power supply is shut off to the other blocks, thereby reducing the electric power consumption to the minimum possible.
However, in the conventional image forming apparatus, a CPU of the image-forming apparatus starts power supply to the function blocks (processing devices) used to carry out a job after receiving a job command from an external computer, and thus may not start the job immediately. Namely, the respective processing devices generally start a preparatory (warm-up) operation in response to turn-on of electric power, and start the job after the preparatory operation has been completed. A certain time period may thus be required to complete the preparatory operation depending on the preparatory operation. For example, in a finisher which glues a cover to the body of bound sheets, if a preparatory operation is carried out to heat and melt solid glue into a liquid or paste state, this preparatory operation takes a long time period.
In this way, the conventional image forming apparatus turns on power supply to the processing devices upon receiving a job command to start the preparatory operation of the processing devices, so that a long time period is required before the preparatory operation is completed, and a job is thus cannot be started immediately.